Python Program to Increment Numeric Strings by K

A numeric string in Python is a string that represents a numerical value using digits, signs, and decimal points, allowing for mathematical operations and data processing. In this article, we will learn different methods to increment numeric strings by K while keeping non-numeric strings unchanged.

Problem Overview

Given a list of strings containing both numeric and non-numeric values, we need to increment only the numeric strings by a given value K ?

Example

Input:

input_list = ["10", "hello", "8", "tutorialspoint", "12", "20"]
k = 5

Expected Output:

['15', 'hello', '13', 'tutorialspoint', '17', '25']

Here, 10, 8, 12, and 20 are numeric strings. After adding K=5:

• 10 + 5 = 15
• 8 + 5 = 13
• 12 + 5 = 17
• 20 + 5 = 25

Method 1: Using For Loop and isdigit()

The isdigit() method returns True if all characters in the string are digits ?

# input list of strings
input_list = ["10", "hello", "8", "tutorialspoint", "12", "20"]
print("Input List:", input_list)

k = 5
result_list = []

# traverse through each element
for element in input_list:
    if element.isdigit():
        # convert to int, add k, then back to string
        result_list.append(str(int(element) + k))
    else:
        # keep non-numeric strings unchanged
        result_list.append(element)

print("After incrementing numeric strings by", k, ":")
print(result_list)

Input List: ['10', 'hello', '8', 'tutorialspoint', '12', '20']
After incrementing numeric strings by 5 :
['15', 'hello', '13', 'tutorialspoint', '17', '25']

Method 2: Using List Comprehension

List comprehension provides a concise way to create lists based on existing lists ?

# input list of strings
input_list = ["10", "hello", "8", "tutorialspoint", "12", "20"]
print("Input List:", input_list)

k = 5

# using list comprehension
result_list = [str(int(element) + k) if element.isdigit() else element for element in input_list]

print("After incrementing numeric strings by", k, ":")
print(result_list)

Input List: ['10', 'hello', '8', 'tutorialspoint', '12', '20']
After incrementing numeric strings by 5 :
['15', 'hello', '13', 'tutorialspoint', '17', '25']

Method 3: Without Built-in Functions

This method manually checks if a string is numeric by examining each character ?

def is_numeric(string):
    """Check if string contains only digits"""
    digits = "0123456789"
    digit_count = 0
    
    for char in string:
        if char in digits:
            digit_count += 1
    
    return digit_count == len(string)

# input list of strings
input_list = ["10", "hello", "8", "tutorialspoint", "12", "20"]
print("Input List:", input_list)

k = 5
result_list = []

for element in input_list:
    if is_numeric(element):
        result_list.append(str(int(element) + k))
    else:
        result_list.append(element)

print("After incrementing numeric strings by", k, ":")
print(result_list)

Input List: ['10', 'hello', '8', 'tutorialspoint', '12', '20']
After incrementing numeric strings by 5 :
['15', 'hello', '13', 'tutorialspoint', '17', '25']

Comparison

Conclusion

Use isdigit() with list comprehension for the most Pythonic solution. The manual approach helps understand the underlying logic, while the for loop method offers the best readability for beginners.